gorann

Thanks Dave! Have to check that info out obviously. I ordered mine from FLO 9th October - wonder if it is a new or old one. In any case I have not had any obvious problems but everything could be improved.

This often imaged NGC object also contains Sh2-171 at the bottom half of the image, and in the upper right quadrant of the image the open star cluster NGC7762 can be seen. It was taken on the evening of Xmas day during a nearly full moon with a dual band filter (Ha & Oiii). Due to the weather it will most certainly be the last catch of the year for me. Taken with the RASA 8 and ASI2600MC and IDAS NBX filter. Gain 100, -15°C. I started off collecting 22 x 5 min but got worried about too many burnt out stars, so changed to 2 min exposures. Got 70 of those before clouds moved in (and have been here ever since). I stacked the two exposure times separately (in PI) but then merged them in PS according to their total exposure time. Together they make up 4.2 hours. EDIT: After posting it looked quite dark so I made a brighter version. EDIT 2: Felt it was a bit too contrasty so I gave it a dose of HDRM Median Transform in PI.

That is a very nice image Wim - I like the colour of the galaxy and you caught a lot of detail. I assume that "LEDA 5061110" is a galaxy. Never herad of that catalog before.

Aha - I forgot I had that one, but it would be nice if it was an atlas rather than a catalogue.

Tried to make an annotation using the list from @wimvb and Aladin Sky Atlas (DSS2) but several of the coordinates in the list do not correspond to a dark patch and there are dark patches (in my image and DSS2, which are very similar) that do not have coordinates in the list. Quite confusing. I also found the Atlas by Dobashi et al 2005 (attached) and the image there (below) does not match my image and DSS2 very well. Maybe the LDN designations are just based on old bad images (like DSS1). Most remarkable is that structure just below LDN1404 which appears to have been missed in Lynds catalog and is not apparent in the Dobashi (DSS1) image. I now also noticed that I forgot to flip my image (RASA produces mirro images) so that is now done. Dobashi Atlas Dark Clouds 2005.pdf

Thanks Wim! Where did you get that list? I will try to make an annotated image from it.

Thanks Richard! Yes, I think I found it surfing on Aladin Sky Atlas. I just wish I had got a few hours on it. I can accept my own stupid misstakes but I hate sabbotage from computers and software.

Thanks Andrew - that was a good description! I may use it for the heading of my next post. "NGC XXX imaged with an obscenely good setup"

Very early on Xmas day morning it cleared here and the moon had fallen below the horizon, so I aimed the RASA 8 with ASI2600MC at this rarely imaged dark nebulosity in Camelopardalis. Googling it gave no images but @wimvb dug out two images on Astrobin. I started at 02.42 but unfortunately I found next morning that my AstroImager had stopped downloading subs and frozen at 04.25. So I only got 16 x 5min subs, so 80 minutes. No filter used. Being an f/2 scope, the RASA still collected enough data to make a relatively presentable image although I really need more data whenever it clears again. Using Aladin Sky Atlas I think I have figured out that LDN1399 is the dark nebula centrally and a bit to the left in the image and LDN1400 is the smaller one just to the right of LDN1399. I have not found any designation for that big dark lump below LDN1400. Stacked in Pi and processed in PS. If anyone knows why AstroImager suddenly stops working on my new Mac Powerbook please tell me. It has now happened a few times.

Gary Imm helped me with some annotations. Thanks Gary!

Thanks Darren!

After nearly a month without seing either the sun or other stars, it finally cleared early Wednesday morning and after the moon had settled I managed to get 64 x 5 min (so 5.3 hours) with the RASA 8 on these darke nebulae in Cassiopeia. Camera was ASI2600MC (no filter). I am not sure which LDN is which and there are also some blue reflection nebulosity in there that probably have designations. Would be nice if someone on SGL can explain what is what in this image🤔 Merry Xmas everyone!

I like the counterweight bar hanging on the back - I assume he has to adjust it according to how much he had for dinner.....

Yes, a Star Adventurer and 90 second exposures so no guiding. That setup will not break you bank (unless you also buy the cooled camera) or back🙂 and you can travel across the world with it. But a HEQ5 will give you more options for the future. An interesting alternative to the Skywatcher ED80 is this one. It costs about the same, it is a true triplet apo, a bit faster (f/6), and more wide field (FL 480 mm). It was my first apo and I still have it: https://www.bresser.de/en/Astronomy/Telescopes/EXPLORE-SCIENTIFIC-ED-APO-80mm-f-6-FCD-1-Alu-2-R-P-Focuser.html

To me that sounds and looks like a success for being the first light. Many says that darks do more harm (add noise) than good for a DSLR since you have no control over the sensor temperature and in your case it was most likely changing a lot due to the falling outdoor temperature.

I echo this recommendation. A great alternative to an ED semi-apo telescope is a used Canon 300 f/4 or 400 f/5.6 lens from the professionald EF series. They are apochromatic lenses with a flat field that will fit directly on your camera. Just see to it that you get the older (and cheaper) model without image stabilizer. On ebay they seem to go for 600 - 700 pounds in the UK (cheaper if you get it from Japan as I did with my 300 f/4). On my Astrobin there are some images I have taken with that Canon 300 f/4, although I used a cooled CMOS (ASI071) rather than a DSLR. Here is an example: https://www.astrobin.com/m5oh8m/F/ And you can of course capture birds with it a daytime🕊️

Yes Valiv, the RASA is cetainly aimed for use with a OSC for RGB or when the moon (or light pollution) is an issue with a OSC and either a dual (or triple?) band filters or a filter slider for NB.

Not sure what fully corrected means here - the spot diagrams suggest to me that is a rather arbitrary concept. In any case, if you turn the ASI1600 90° then two panels would approximately cover the same FOV, and 4 panels would certainly cover much more.

When you say the RASA will have to make a 2x2 mosaic, then I get a bit confused. Do you mean that you have a camera with a 44 mm diagonal on the Tak, so a full frame APS? Then, taking the FL into account the FOV is still not that different. Here is a comparison of the Tak with an ASI6200 (44 mm diagonal) and the RASA 8 with an ASI2600 (28 mm diagonal):

Very interesting comparison Vlaiv. If I get it right, the Tak FSQ 106 f/5 has about the same resolving power that the RASA 8 f/2, but then needs 4 times longer to gather the same amount of photons (counting aperture area) or even 6-times as counted from f-value. They weigh the same but the FSQ 106 costs 3.3 times more.

"In outer field SharpStar 200 F/3.2 is as sharp as 30.3mm of aperture. " 30 mm aperture is like a small handheld binocular. It cannot be that bad so I must miss something here about what aperture here means. Also, what about the Tak apos, their airy disks did not seem much smaller than those of the mirror scopes.

Thanks a lot Vlaiv! It clarified several thing, not the least that diffraction limited means that the spots should be within the airy discs. I assume the circles in the Sharpstar diagrams are not airy discs, but the circles for the RASA 8 may be airy discs.

Yes, the others have a wider image circle. In the case of RASA 8 a wider image circle would mean that a bit too much of the 8" front lens would be centrally obstructed. About the RASA 8 Celestron/FLO says "whilst ~22mm diagonal is optimal the RASA 8 can also be used with larger sensors up to 32mm diagonal, including the APS-C sized sensors, though some compromise must be expected at the image periphery." With my ASI2600 that has a diagonal of 28 mm the corners are quite acceptable.

Does anyone have a feeling for what a good spot diagram should look like? I think @vlaiv have suggested that the RASAs are not diffracton limited and referred to a spot diagram. Still I am impressed with the resolution of my RASA 8, an example of which is the Tadpole nebula that I recently posted, a resolution which even impressed @ollypenrice. So this rainy Sunday afternoon I started googling spot diagrams and found them for RASA 8, RASA 11, Tak Epsilon 180, Sharpstar 150 and 200. In addition I found some for Tak Apo refractors for comparison. Starring at these spots actually gave me a headache as I found them difficult to figure out and compare. The fact that Tak and Sharpstar put their spots into 40, 50 or 100 um squares while Celestron use 18 um squares did not make a straight visual comparison easy. I think my preliminary conclusion is that the RASAs are quite comparable to the Epsilon, if anything they have smaller spots. The Sharpstars have bigger spots as far as I can tell. What surprised me the most was that the spots of the Tak Apos did not seem to be much smaller than these mirror astrographs, but I am probably missing something here. I could not easily find any spot diagrams for the very expensive Riccardi Honders astrographs. Comments most welcome, not the least from someone less ignorant about spot diagrams than me. Cheers, Göran RASA 8 f/2: RASA 11 f/2.2: Epsilon 180 f/2.8 Sharpstar 150 f/2.8 Sharpstar 200 f/3.2 Tak FSQ 106 f/5 Tak FS & TSA 102 f/8

Yes, mine is working again, so thanks a lot Salvatore! I noticed that a few hours without Astrobin lead to severe abstinence symptoms, so you have created a new addiction😁